Speeding Up and Slowing Down Acceleration and Deceleration

ACCELERATION Change in VELOCITY occurring over TIME Units: METERS PER SECOND2 VECTOR Negative Velocity Negative Velocity Positive Velocity Positive Velocity Negative Acceleration Negative Acceleration Positive Acceleration Positive Acceleration Slowing down Eventually speeds up in + direction! Slowing down Eventually speeds up in – direction! Speeding up in + direction Speeding up in - direction

Equations An object’s velocity at any point in time can be found by considering: - its starting velocity its acceleration the amount of time over which it accelerates Acceleration is the rate of change in velocity over time Subscript f = “final” Subscript i = “initial”

Tips on Solving Problems In order to receive full credit on tests and quizzes, including the Regents Test, you have to include the following in your answer: The equation you will use The given values WITH UNITS The correct answer WITH UNITS *99% of the time, if there is a number it HAS UNITS ** Units for a certain number have to appear at least ONCE in your solution

2 Methods A car travels 100 meters in 20 seconds, calculate its velocity. Recommended Method Alternative Method

Example Two cars start at the same point. Car A starts with a velocity of -5 meters per second while Car B starts with a velocity of +3 meters per second. At the end of 15 seconds, Car A has a velocity of +25 meters per second. Calculate Car A’s acceleration

Example Two cars start at the same point. Car A starts with a velocity of -5 meters per second while Car B starts with a velocity of +3 meters per second. At the end of 15 seconds, Car A has a velocity of +25 meters per second. If Car B has the same acceleration, determine its speed at 15 seconds

SUMMARY Acceleration Describe the 2 methods to solve problems Definition? Vector or Scalar? Units? Equations? Describe the 2 methods to solve problems